I was wondering if one of you fine folks could point me in the right direction.I am trying to source the large 4000MFD 80VDC filter caps found in a M-400t cube amp. (newer style power supply)My caps have vented so I am on a mission to replace the opto-coupler and the filter caps.

Any resources would be highly appreciated.I use this amp as a primary driver in my studio.I have had to resort to using a Kenwood receiver I had lying around my garage. Uggghhhh.

first and foremost, welcome. as the 80 volt venue is limited, i would suggest using a stantard 100v cap instread. the bob father has long ago approved of this. you can sub a part that is close and over volt rating is ok. the cap will form itself to what is needed.

My first inclination was to look into Digikey, Mouser, Newark etc.With the disappointing results I found there I was prompted to look around for user groups that love Carver products.A little "Googling" brought me to this site.

This is what I looked for:Electrolytic Cap: 4000MFD: 100-150 Volts: Can Type with Screw Terminals.

There are a number of good candidates that popped up BUT the 100 VDC caps are 2 inches in diameter.The 150 VDC caps are even larger at 3 inches.So unless I can find a similar dimension cap, even one that I can solder in place, it looks like I will have to do a Frankenstein to get my trusty M400 running again. I might even have to create a bank of four or more smaller diameter caps to get the equivalent reserve.

This is going to sound insane to some, maybe not so insane to others.If I have to Frankenstein this amp I don't think I will ever be happy with it. Why? Because I know under that slick aluminum cover will be a patch job at best. It's like putting a V6 motor where a V8 used to be. Sure it will work but by doing so the value of the car has been diminished. Just call me nuts.....really....I don't mind.

Have any of you modded or installed newer caps of different dimensions in a M400t? I would love to see pics and part numbers if possible.

Thanks!

Now another really interesting question comes to mind. I see this over and over again in TV power supplies. Caps exploded because they are operating at the fringe of their rated capacity. I almost always bump the voltage up when replacing them and the equipment runs great for years to come. Why is this the norm? For example, in the M400, if the TRIAC fails in a conducting state then the caps are going to see a charging voltage greater than 80 volts. This is well known. Then why not build it with caps that exceed the highest voltage the caps could ever see, whether the charging circuit is operating under normal or abnormal conditions? Is it purely cost that drives this? Or is there some other factor about the charging or discharging characteristics of higher voltage caps?

Not ten minutes after I entered my last post I decided to widen my search parameters a little.

Now I can find 35mm diameter capacitors. The voltages are from 100 to 120 VDC. I can live with the higher voltages, in fact I really like the idea that the caps are a little more robust.

The problem lies in the capacitance. 4000 MFD is not an option. However I could either go 3900 MFD or 4700 MFD.My gut is saying go with 4700 MFD for a little more storage capacity but I am no power supply engineer.

For those of you who have some experience with repairing Carver equipment I please need a nudge in the right direction.This unit has a new style rev 7 power supply

I was so excited today.I got two new really nice looking main caps for my M400.I also ordered some spare opto couplers (Fairchild CN17-1)

My old caps had vented over time so there was a lot of residue to clean up.I installed the new OC1Installed the new caps.Put the amp on a variac and brought it up to 95 VAC. (Just under the rating of the new caps)I was expecting to see @ 75VDC on the rail (collector of large Q6) but it was just way off. It is much too high.The voltage just seemed to follow variac voltage. It would increase and decrease with the adjustment of the variac. It never stabilized somewhere around 75VDC.Adjusting pot RP2 has no effect on 75V rail.I kept the variac turned down to a safe level to prevent venting the new caps.

So now I am stuck.I looked at small transistors Q5 and Q6 on the PS board and they test OK.Pot RP2 tests fine.12+ and 12- test fine.Putting a scope on the center pin of the triac shows what appears to be a normally chopped up sine wave.

generatorlabs, for more "horsepower" (or just more eyes on the problem), I'd suggest that you also post your issue at thecarversite as well. They have chased away/alientated some pretty knowledgeable folks (electronics wise..) over there, but still some left that will be able to most likely solve your problem. Not saying that a bunch here could not, but sometimes they just don't have the time...

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